1. Field of the Invention
The present invention relates to a computer-readable storage medium, an image display apparatus, system, and method; and in particular, relates to a computer-readable storage medium, an image display apparatus, system, and method for stereoscopically displaying a virtual object on a screen of a stereoscopic-viewing-enabling stereoscopic display device.
2. Description of the Background Art
In recent years, there has been advances in the research of AR (Augmented Reality) technology which enables displaying a virtual object as if it actually exists in the real world by combining and displaying the virtual object with an image of the real world.
For example, in a stereoscopic display device disclosed in patent literature 1 (Japanese Laid-Open Patent Publication No. 2008-146109), images taken respectively by a right-eye camera and a left-eye camera attached to a head mounted display are used to obtain respective relative positions and attitudes of the right-eye camera and the left-eye camera with regard to a marker disposed in the real space, and based on the obtained result, an image of a virtual object for the right eye and an image of the virtual object for the left eye are respectively generated. Then, the images respectively taken by the right-eye camera and the left-eye camera are respectively combined with the image of the virtual object for the right eye and the image of the virtual object for the left eye, and the combined images are respectively displayed on a right-eye LCD (liquid crystal display) and a left-eye LCD.
In addition, non-patent literature 1 (Hirokazu Kato, Mark Billinghurst, “Marker Tracking and HMD Calibration for a Video-Based Augmented Reality Conferencing System,” IWAR, pp. 85, 2nd IEEE and ACM International Workshop on Augmented Reality, 1999) discloses a method for calculating relative positions and relative attitudes of a camera and a marker in the real world, based on the position and attitude of the marker in an image taken by the camera.
With the stereoscopic display device disclosed in patent literature 1, basically, the virtual object is merely stereoscopically displayed such that the virtual object appears to be at a position identical to the marker. However, for example, when another virtual object is arranged at a position that appears to be considerably closer in the foreground than the marker, and when an image of this virtual object arranged at a position away from the marker and an image of the virtual object arranged at the position identical to the marker are both taken by a virtual camera, there are cases where a difference between an amount of display-deviation (an amount of display-deviation that enables stereoscopic vision) on the screen for one of the virtual objects and an amount of display-deviation on the screen for the other virtual object becomes large, and thereby making it difficult for the user to view the virtual objects.